In the rotary machining of hard-brittle or difficult machinable materials such as ceramics, glass or hard metals, the cutting tool may be exposed to loads that are so high that it is subject to premature wear. In order to extend the tool life, it is known practice to superimpose ultrasonic oscillating movements to the rotational tool movement, thereby transmitting ultrasonic oscillations to the tool or the workpiece, respectively. This results in a modification of the machining cinematics while the ultrasonic oscillations have an advantageous influence upon material removal.
Tool assemblies that are suitable for such a combined machining are known from the references DE-A1-41 03 569 (corresponding to U.S. Pat. No. 5,144,771) and EP-A1-591 104 (corresponding to U.S. Pat. No. 5,361,543). These known assemblies suffer from the disadvantage that they cannot be held in current tool spindles so that the machine tool must be specially designed for using such a tool assembly. It is therefore impossible or difficult to also use other tools, e.g. tools that are exclusively intended for rotary machining operations, in the same machine tool. In particular, the known tool assemblies are unsuitable for retrofitting an existing machine, e.g. a circular grinding machine, in a simple manner so that ultrasonically assisted machining operations are also possible. Furthermore, the tool assemblies of the prior art are relatively bulky and therefore unsuitable for being used at high rotational speeds of the tool spindle.